Tension and frustration is mounting as families wait for any morsel of news about the whereabouts of Malaysia Airlines Flight MH370 and the fate of their loved ones. Mental health experts say it is the not knowing that compounds their unresolved grief.

It’s been four days since the flight between Kuala Lumpur and Beijing went missing with 239 passengers and crew on board. An international search of large swaths of ocean on either side of the Malay Peninsula has turned up no evidence of the lost Boeing 777.

“The hardest thing for human beings to deal with is the unknown,” said Ann Rosen Spector, a clinical psychologist from Philadelphia who specializes in grief. “If you look at science, religion or logic, it’s about explaining the unknown. We always want to complete the circle. It’s like a scab is ripped off every time another piece of information takes away the hope.”

“First of all, they are dealing with conflicting reports,” she said. “Every time you start to hold on to one piece of information, there is something else that is 180 degrees different. They don’t have any place to put their anger or pain and keep getting the hope that something else will happen, a miracle to undead the person.”

Conspiracy theories – from terrorism to a potential hijacking or even pilot suicide -- fueled the rumors as families waited for news in Beijing and Kuala Lumpur.

Some relatives held on to hope, telling authorities that they were able to call the cellphones of their relatives, and were not sent to voice mail, possible proof that they were still alive. Others said they found their instant messenger accounts on the Chinese online service QQ were active.

“Death is always something hard to wrap your head around – the finality of it – and every variable that takes you away from what would bring closure is that many degrees harder,” said Rosen.

She cited the forced disappearances of an estimated 30,000 people in Argentina in the 1970s and 1980s, as well as the confusion about survivors after the World Trade Center terrorist attacks in 2001.

“It’s always hard when you can’t complete the rituals and don’t have a body,” said Rosen. “The same thing happens when war servicemen go missing – you don’t know where they died or how they died and you are left with the idea that they will return one day.”

Kenneth Doka, a professor of counseling at the College of New Rochelle in New York, said that families desperate for information “want a story that makes sense.”

“Whenever there is a sense of trauma, people want to have a narrative, a sense of what happened and why it happened," he said. “It’s an unfinished story when you have unanswered questions. It complicates the grieving.”

Narratives, particularly heroic ones, can help people deal with trauma.

When United Airlines Flight 93 crashed into a field Shanksville, Pa., after terrorists hijacked the plane on 9/11, passengers reportedly fought to regain controls by breaching the cockpit and overpowering the flight crew. Todd Beamer’s now infamous words, “Let’s roll,” gave families of the 44 passengers who died a way to embrace the loss, according to Doka.